Layered diaphragm

ABSTRACT

A carburetor may have a fuel metering assembly with a metering valve and a metering diaphragm sealed to a body of the carburetor to at least partially define a metering chamber with a portion of the metering diaphragm movable relative to the body to actuate a fuel metering valve. The diaphragm may include a continuous layer, a discontinuous layer, and an intermediate layer received at least partially between the continuous and discontinuous layers and at least partially inhibiting direct contact between the continuous and discontinuous layers. The continuous and discontinuous layers may be different polymer materials and the intermediate layer may be a polymer different than that of the discontinuous layer. The intermediate layer may include voids, segments, or a wire form.

REFERENCE TO RELATED APPLICATION

This patent application claims the benefit of the earlier filed U.S.provisional patent application, Ser. No. 62/243,857, filed on Oct. 20,2015, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to carburetors and diaphragmsfor use with carburetors.

BACKGROUND

Carburetors are devices that can be used to mix fuel with air to powercombustion engines typically including gasoline powered internalcombustion engines. A carburetor may include a fuel metering system thathelps to control the amount of fuel supplied to air flowing through apassage of the carburetor for mixing the fuel with air and supplying itto the engine. Some metering systems employ a diaphragm that oscillatesor reciprocates during operation to open and close a metering valveadmitting fuel to a chamber from which it is supplied to the passage formixing with air. The large number of cycles experienced by suchdiaphragms, when combined with physical interaction with other meteringsystem components and continuous exposure to solvent-containing fuelscan result in a harsh operating environment that causes wear anddegradation of the diaphragm. In a spark ignited internal combustionso-called small engine the diaphragm must fully open the valve with asmall pressure differential which is typically not more than negative(−)0.9956 kPa or −10.16 gf/cm² and usually about a −0.50 kPa or −5.0gf/cm².

SUMMARY

In at least some implementations a carburetor has a metering system thatcontrols gasoline fuel flow from a source to an air-fuel mixing passagefor delivery to a gasoline powered spark ignited internal combustionengine. A metering system may include a metering diaphragm sealed to abody of the carburetor to at least partially define a metering chamberbetween the diaphragm and the body with the metering diaphragm having aportion that is movable relative to the body to actuate a meteringvalve. The metering diaphragm may include a continuous layer, adiscontinuous layer, and intermediate layer received at least partiallybetween them. In use, the continuous layer may be responsive to a fluidpressure differential to move the intermediate layer to cause thediscontinuous layer to open and close the metering valve to allow fuelflow from the fuel source into the metering chamber. The intermediatelayer may include a periphery trapped between two carburetor bodies andbetween a periphery of the continuous and discontinuous layers. Theintermediate layer may include a void, a segment or a wire form. Theintermediate layer may at least substantially inhibit direct contactbetween the continuous and discontinuous layers at least in the portionof the diaphragm that moves to open the metering valve.

The intermediate layer may have portions or segments underlying at leastportions of the discontinuous layer and voids complimentary to voids inthe discontinuous layer. Portions of the intermediate layer may be widerthan corresponding portions of the discontinuous layer. The continuousand discontinuous layers may be of a different polymer material and theintermediate layer may be a polymer material different than that of thediscontinuous layer. The intermediate layer may be less abrasive,softer, and/or have a smoother surface than the discontinuous layer. Theintermediate layer may be bonded to the discontinuous layer and/or thecontinuous layer.

A carburetor may have first and second bodies, a fuel chamber, and amultilayer diaphragm received between the body with a discontinuouslayer, a continuous layer, and an intermediate layer disposed betweenthem and which, when in use, the discontinuous layer flexes to actuate afuel flow valve, the continuous layer divides a portion of the fuelchamber and moves in response to a pressure differential and theintermediate layer at least substantially inhibits direct contact of thediscontinuous layer with the continuous layer at least within the fuelchamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of preferred embodiments and bestmode will be set forth with reference to the accompanying drawings, inwhich:

FIG. 1 is a schematic cross-sectional view of a carburetor with adiaphragm metering system, according to one embodiment;

FIG. 2 is a partially exploded view of one embodiment of a carburetorwith a layered metering diaphragm;

FIG. 3 is an alternative embodiment of a continuous layer of themetering diaphragm of FIG. 2, including a bagged portion;

FIG. 4 is an alternative embodiment of a discontinuous layer of themetering diaphragm of FIG. 2, including a contact portion with aprotrusion;

FIG. 5 is a plan view of the discontinuous layer of the meteringdiaphragm of FIG. 2;

FIG. 6 is a plan view of another embodiment of a discontinuous layer,including radial slots;

FIG. 7 is a plan view of another embodiment of a discontinuous layer,included arc-shaped slots;

FIG. 8 is a plan view of another embodiment of a discontinuous layer,including a C-shaped slot;

FIG. 9 is a plan view of another embodiment of a discontinuous layer,including a conductive path;

FIG. 10 is a plan view of another embodiment of a discontinuous layer,including a differently configured conductive path;

FIGS. 11-14 are plan views of various other discontinuous layers;

FIG. 15 is a perspective view of another embodiment of a discontinuouslayer that includes a wire form;

FIG. 16 is a partial cross-sectional view of a carburetor including thediscontinuous layer of FIG. 15;

FIGS. 17-23 depict additional embodiments of discontinuous layersincluding wire forms;

FIG. 24 is a partial cross-sectional view of a carburetor with anotherembodiment of a diaphragm metering system;

FIG. 25 is a partial cross-sectional view of a carburetor with adiaphragm fuel pump;

FIG. 26 is a side view of an illustrative process for making a diaphragmsubassembly;

FIG. 27 is a plan view of the process of FIG. 26;

FIG. 28 is a plan view of a dynamic portion of a diaphragm fuel pump,including a diaphragm and flapper valves;

FIG. 29 is a cross-sectional view of the diaphragm of the component ofFIG. 28 when installed in a carburetor;

FIG. 30 is a cross-sectional view of one of the flapper valves of thecomponent of FIG. 28 when installed in a carburetor; and

FIG. 31 is an exploded view of a multi-layer diaphragm including acontinuous layer and more than one discontinuous layer.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS

As will become apparent from the following disclosure, a carburetor forproviding fuel to a combustion engine may be equipped with a diaphragm,such as a metering diaphragm, that has an effective stiffness orresistance to movement that varies as a function of one or more factors.For example, the effective stiffness can vary with the amount ofmovement, flexing or deflection of the diaphragm, similar to a spring.To achieve this characteristic, the diaphragm may include adiscontinuous layer that is attached at a periphery of a meteringchamber. The diaphragm may also have a resistance to movement that isaffected by the presence, application, and or magnitude of an electricor magnetic field. For example, the diaphragm may include a conductiveportion across which a voltage may be applied to affect diaphragmmovement or to which a magnetic field may be applied to affect diaphragmmovement. Such conductive portions can be useful to monitor certaincarburetor conditions and/or tune the carburetor during operation.

Referring in more detail to the drawings, FIG. 1 is a cross-sectionalview of a carburetor 10 with a diaphragm metering system 12. Many of theindividual components and arrangement of components in FIG. 1 are shownschematically for illustration purposes—i.e., the cross-section does notnecessarily represent a planar cross-section through an operablecarburetor and may omit one or more carburetor components or features.The carburetor 10 includes a body 14 and an air-fuel passage 16 formedthrough the body. The body 14 supports the metering system 12, which isconstructed and arranged to help control fuel flow from a fuel source 18to the air-fuel passage 16. In this particular embodiment, the fuelsource 18 is a passage that is in fluid communication with a pumpchamber of an onboard fuel pump 20. The fuel pump 20 may be a diaphragmtype fuel pump or any other type of fuel pump capable of providingand/or pressurizing fuel at fuel source 18. The fuel source 18 maysimply be a port in the carburetor body arranged for connection withgravity-fed fuel, in a different embodiment.

In the illustrated embodiment, the carburetor body 14 includes fluidpassages 22, 24 formed therein to accommodate fuel flow from the fuelsource 18 to the passage 16 during carburetor operation. A recess 26 mayalso be provided in an outer surface of the carburetor body 14 to partlydefine a metering chamber 28 fluidly connecting the fluid passages 22and 24. Skilled artisans will appreciate that the carburetor 10 mayinclude other components or features such as a cover 30, a throttlevalve 32 (shown as a dashed line in a partially open position), as wellas other components not shown. For example, the carburetor may includeone or more additional fluid passages, a choke mechanism, and/or an airpurge mechanism, among other things. The illustrated passages are onlyrepresentative and may each comprise multiple individually formedpassages to allow fluid flow between respective portions of thecarburetor.

The metering system 12 includes a metering diaphragm 40 and a meteringvalve 42. The metering diaphragm 40 has a chamber side 44 and anopposite reference side 46. The chamber side 44 and the carburetor body14 together form the metering chamber 28. The metering diaphragm 40 isattached to the carburetor body 14 to form a fluid tight seal 34 about aperiphery 36 of the metering chamber 28. In the example of FIG. 1, anoptional gasket 38 is located about the periphery 36 to partly form theseal 34, and at least a portion of the diaphragm 40 is fixed at theperiphery 36 between the carburetor body 14 and the cover 30. The cover30 is optional and may include a port 70 formed therethrough to allowatmospheric or another reference pressure to act upon the reference side46 of the diaphragm 40. The diaphragm 40 may be sealed to the body 14 byother means, such as a bead of adhesive or a weld at or about theperiphery 36, and the seal 34 need not include both layers of thediaphragm along the entire periphery.

In operation, the metering diaphragm 40 moves in response to pressuredifferentials to actuate the metering valve 42. In the illustratedembodiment, a reference pressure (e.g., atmospheric pressure) acts uponthe reference side 46 of the diaphragm 40, and fluid pressure in themetering chamber 28 acts upon the chamber side 44 of the diaphragm 40.As air flows from the atmosphere and through the passage 16 to be mixedwith fuel on its way to the engine, the pressure in the air-fuel passage16 and the metering chamber 28 falls below the reference pressure asfuel is delivered from the metering chamber to the passage 16. Thediaphragm 40 deflects of flexes in a direction that decreases the volumeof the chamber 28 to open the metering valve and allow fuel to flow fromfuel source 18 and into the chamber 28 through passage 22. When thechamber pressure is equalized with and/or exceeds the reference pressuredue to the newly introduced fuel in the metering chamber 28, thediaphragm 40 moves in the opposite direction, and the metering valve 42closes until metering chamber pressure again falls below the referencepressure as fuel is provided to the air-fuel passage 16. Thus, everytime a dose of fuel is delivered from the metering chamber 28 to theair-fuel passage 16, the metering valve 42 is opened to refill themetering chamber 28 then closed again until the next dose of fuel isdelivered to passage 16.

In the embodiment of FIG. 1, the diaphragm 40 actuates valve 42 via thecombined actions of various other components, including a metering lever48, a pivot 50, a metering spring 52, and a stem 54. The valve 42includes a valve body 56 and a valve seat 58 and may be a poppet valveas illustrated or any other type of valve. In the illustratedarrangement, diaphragm movement pivots the lever 48 about the pivot 50in opposition to the spring 52 to move the valve body 56 away from valveseat 58. As the metering chamber pressure is equalized with thereference pressure and the diaphragm 40 moves in a direction away fromthe metering lever 48, the spring 52 acts to pivot the lever 48 in theopposite direction to reseat the valve 42. Skilled artisans willappreciate that this is only one example of components arranged to allowthe diaphragm 40 to actuate valve 42. For example, the valve body 56could move away from the valve seat 58 in a different direction, adifferent portion of the diaphragm 40 could contact the metering lever,etc.

The metering diaphragm 40 may serve several functions, such as, but notlimited to, partly defining the metering chamber 28, flexing orotherwise moving in response to changing fluid pressure differentialsacross its opposite sides and/or physically contacting other meteringsystem components. It also should be resistant to chemical attack fromfuels. In one embodiment, such as that shown in FIG. 1, the meteringdiaphragm 40 is a layered diaphragm including layers 60 and 62. As willbe described in further detail below, each layer of the layered meteringdiaphragm can be constructed from different materials and/or withdifferent characteristics to together perform diaphragm functions.

Layer 60 of the diaphragm may be a continuous layer of flexible materialresponsive to the above-described fluid pressure differentials. As usedhere, a continuous layer is a layer that is uninterrupted by holes,apertures, openings, or other components extending therethrough. Layer60 may also be described as a film or membrane and may be present at theseal 34 along the entire periphery 36 of the metering chamber 28. Layer60 oscillates in response to metering chamber pressure changes whetheror not additional diaphragm layers are employed and is constructed sothat fuel cannot flow through it. Layer 62 of the diaphragm may be adiscontinuous layer of material and may be provided to physicallycontact other metering system components (e.g., metering lever 48) toactuate the metering valve 42. As used here, a discontinuous layer is alayer of material through which or around which fuel can flow. Forexample, the discontinuous layer 62 may include one or more slots 72 orother openings formed at least partially therethrough. In someimplementations, layer 62 is affixed to the carburetor body 14 along atleast a portion of the periphery 36 of the metering chamber. By affixedit is not intended to mean only a direct connection such as by afastener or adhesive, restricting movement of a part of the layerrelative to the carburetor body is sufficient which may be done in manyways such as simply holding the layer against the carburetor body,clamping it against the body with another component or otherwiserestricting movement of a part of the layer relative to the carburetorbody.

The metering diaphragm 40 may be constructed so that one of theindividual layers 60, 62 is configured to perform certain diaphragmfunctions without regard for other diaphragm functions, while the otherone of the individual layers 60, 62 is configured to perform otherdiaphragm functions. For example, continuous layer 60 may be constructedas a thin, flexible membrane layer that quickly responds to meteringchamber pressure changes without regard for its ability to endure aproduct lifetime of wear where the diaphragm 40 physically contactsand/or moves against other metering system components. Likewise, thediscontinuous layer 62 may be constructed as a wear-resistant elementthat is capable of withstanding a product lifetime of physical contactand/or movement against other metering system components without regardfor its ability to quickly respond to metering chamber pressure changesor to form a seal at the interface between the diaphragm 40 and the body14 on its own. Of course, the continuous layer 60 may employwear-resistant materials, and the discontinuous layer element 62 may bemade from membrane-like materials. Particular non-limiting examples ofmetering diaphragms having multiple layers will be described below.

FIG. 2 is a partially exploded view of a carburetor 10 with a meteringsystem 12, according to one embodiment. Carburetor 10 includes a mainbody 14, through which the air-fuel passage 16 is formed, and anintermediate body 15 connected to the main body 14. In this particularembodiment, a diaphragm-type fuel pump (hidden from view) is providedbetween bodies 14 and 15 and provides the fuel source for meteringsystem 12. Alternatively, the fuel pump may be omitted and fuel lineconnector 25 may act as the fuel source for the metering system undergravitational pressure. A recess 26 formed in the intermediate body 15defines part of the metering chamber. Recess 26 is fluidly connected tothe air-fuel passage 16 via one or more passages in each of the bodies14, 15. This embodiment also includes an air purge system 35 forremoving air from the metering chamber and priming the carburetor withfuel for start-up. Though the particular cover 30 shown in FIG. 2 mayinclude various arrangements of valves and passages as part of the airpurge system 35, it is similar to the cover 30 of FIG. 1 in that itcovers the metering diaphragm 40 and forms a cavity or reference chamberbetween itself and the diaphragm 40 that resides at a reference pressure(e.g., atmospheric pressure).

The illustrated metering diaphragm 40 includes a continuous layer 60 anda discontinuous layer 62. Each layer 60, 62 spans across or extends overrecess 26 and is shaped so that each layer 60, 62 is present at the sealformed at the periphery 36 of the metering chamber in thisimplementation. Both of the layers 60, 62 are fixed between the cover 30and the body 14 along the entire periphery 36 of the metering chamber inthis embodiment, and each layer extends outside of the periphery 36 toaccommodate various through-holes and/or locating features 74 and toprovide a portion of the diaphragm for clamping between the body 14 andthe cover 30. A similarly shaped gasket 38 is also provided in thisexample, but is not always necessary.

The continuous layer 60 may be constructed from a polymeric film orsheet material. Suitable materials for the continuous layer may includepolytetrafluoroethylene (e.g., Dupont Teflon), polyesters (e.g., DupontMylar), fluoroelastomers (e.g., Dupont Viton), low density polyethylene(LDPE), nitrile rubber (e.g., Parker N1500-75), or polyurethanes such asTPUs, though other materials may be utilized. Material selection may bebased on numerous factors such as resistance to the particular fuelsused with the carburetor (e.g., gasoline, ethanol, and mixturesthereof), cost, and ease of forming. Where layer 60 is a continuouslayer, material choices are not limited to known diaphragm materialsthat are sometimes selected partly for their ability to accommodate athrough-hole and form a seal at the through-hole with a contact elementthat extends therethrough. Though woven materials or other types oftextile fabrics impregnated with elastomeric materials may be used forcontinuous layer 60, these types of composite materials are notnecessary. In one embodiment, layer 60 is a continuous layer ofnon-woven polymeric material. In another embodiment, layer 60 is ahomogeneous layer of polymeric material.

Depending on material stiffness and other factors, the continuous layer60 may have a thickness in a range from about 0.001″ to about 0.010″.Generally, a thinner continuous layer 60 will be more responsive topressure changes in the metering chamber for a given material, but thelayer should also be sufficiently thick to endure cyclic fatigue and tohave sufficient integrity to move the discontinuous layer 62 duringoperation. In one particular embodiment, the continuous layer 60 isformed from a sheet of TPU material having a generally uniform thicknessin a range from about 0.001″ to about 0.005″, or about 0.003″ onaverage. The continuous layer 60 may be die-cut from sheet stockmaterial, injection molded, or otherwise formed.

With reference to FIG. 3, another embodiment of the continuous layer 60′includes a bagged portion 65 located within the periphery 36 of themetering chamber. The bagged portion 65 is characterized by a thicknessthat is less than the nominal thickness of the layer (e.g., thethickness in the region surrounding the bagged portion 65) and/or anincreased surface area compared to the same region of the layer if itwas flat. The overall range of movement of layer 60 may also beincreased when configured with a bagged portion.

The bagged portion 65 can be formed in layer 60 by controlled stretchingof the layer 60 before or after assembly. For example, after assembly,the metering chamber of the carburetor may be sealed-off by closing anyvalves along fluid passages connecting the metering chamber to otherportions of the carburetor, and the metering chamber may be pressurizedto a level sufficient to plastically deform the continuous layer 60. Thepressurization may be positive or negative. In one embodiment, a baggedportion is formed in the continuous layer of the metering diaphragm inthis manner, and may be formed during metering chamber leak testing, forexample. This technique may be used to form the bagged portion in thecontinuous layer even in the absence of additional diaphragm layers.Similar fluid pressure stretching or mechanical stretching of thecontinuous layer may be performed prior to assembly as well.

Referring again to FIG. 2, layer 62 is a discontinuous layer in thisimplementation, including one or more discontinuities such as voids(e.g. slots) 72 formed at least partially therethrough. The voids orother discontinuities can be formed fully through the layer 62 or onlypartially through resulting in portions of the layer 62 having differentthickness than other portions. In this particular example, threeindividual slots are included through layer 62 in a spiral patternsurrounding a centrally located contact portion 76. The contact portion76 is the portion of diaphragm 60 that physically contacts othermetering system components such as the metering lever 48. The slots 72are provided to allow the discontinuous layer 62 to more easily deflect.In other words, without the slots 72, layer 62 may be too stiff to movewith the continuous layer 60 to actuate the metering valve because itmay be configured to have sufficient strength and integrity to endurecontinuous cycling and contact with the metering lever 48. The slots 72can be arranged in any manner that allows at least the contact portion76 of layer 62 to move freely with the continuous layer 60 when itresponds to pressure changes in the metering chamber. In one embodiment,each of the layers 60, 62 has a range of movement of about 2.0 mm ormore from a planar datum A, datum A being located between and generallyparallel with flat portions of layers 60, 62 at the periphery of themetering chamber 28 (shown best in FIG. 1).

The discontinuous layer 62 can be configured to provide the diaphragm 40with any desired resistance to movement by configuring the slots 72accordingly. For example, for a discontinuous layer 62 with spiralslots, the spiral arms (i.e., the material between the slots) may bedesigned longer or shorter to respectively decrease or increase theresistance to movement of the discontinuous layer 62 and the diaphragm40 as a whole. This resistance to movement can be expressed in terms offorce per unit distance, such as N/mm or lbs/in, much like a spring. Inone embodiment, the metering system includes a metering spring, and acharacteristic spring rate or effective stiffness for the discontinuouslayer is about 50% of the spring rate of the metering spring or less. Inanother embodiment, the characteristic spring rate of the discontinuouslayer is about 25% of the metering spring rate or less. These relativelylow characteristic spring rates can help minimize the effect that othervariables such temperature, age, fuel type, manufacturing tolerances,etc. have on the overall performance of the carburetor so that themetering spring remains largely responsible for metering systemperformance.

The discontinuous layer 62 of the diaphragm may be constructed fromnearly any material, including plastic or metal materials. Suitablematerials for layer 62 may include polyacetal (e.g., Dupont Delrin),polyester (e.g., Dupont Mylar), or stainless steel, though othermaterials may be utilized including combinations of metal and plastic insome cases. Material selection may be based on numerous factors such asfuel resistance and wear resistance, to name a few. Depending onmaterial stiffness, slot configuration, and/or other factors, layer 62may have a thickness in a range from about 0.003″ to about 0.040″. Forexample, a plastic discontinuous layer 62 may be generally thicker thanthe continuous layer 60, ranging from about 0.005″ to about 0.040″thick. In one embodiment, layer 62 is a discontinuous layer that has athickness in a range from about 0.015″ to about 0.025″, or about 0.020″nominal. When constructed with stiffer metal materials, the thickness oflayer 62 may be less than with plastic materials, such as from about0.003″ to about 0.015″. Of course, the configuration of the slots 72 inlayer 62, when included, may affect these non-limiting ranges.

Layer 62 may be die-cut, laser-cut, injection molded, stamped, orotherwise formed. In some embodiments, including that shown in FIG. 2,the outer perimeter of both of layers 60 and 62 may have the sameoverall shape, and each may include one or more corresponding locatingfeatures and/or through-holes 74 that line up with correspondingfeatures on the carburetor body 14 and/or with the gasket 38 whereprovided. In one particular embodiment, illustrated in FIG. 4, thediscontinuous layer 62′ includes a protrusion 76′ at the contact portionof the layer. The protrusion 76′ may be integrally formed in the samepiece of material as the rest of the layer 62′ (e.g., by injectionmolding in plastic or by stamping a proud feature in metal) or may be aseparately attached piece. This type of configuration simulates a“button” feature and may allow for a metering lever 48 that is simplerwith less bends formed therein.

Layered metering diaphragms such as those described above can allowdiaphragm materials to be selected according to their respectivefunctions for improved performance while additionally simplifying and/orlowering the cost of manufacturing metering diaphragms over conventionalmetering diaphragm constructions. For example, the continuous layer 60does not necessarily require a hole to be formed therethrough forattachment of other metering system components, thus reducing theinitial and long-term likelihood of fuel leaks through the diaphragm. Infact, the two diaphragm layers 60, 62 need not be attached together atall. While the layers 60, 62 may be optionally attached together,configuring layer 62 to be attached at the periphery of the meteringchamber allows it to be separate from the continuous layer 60, at leastin the region of the contact portion 76 of layer 62. Affixing thediscontinuous layer 62 at the periphery of the metering chamber may alsoallow for the use of metering springs with relatively low springconstants, thereby allowing for a metering system that is more sensitiveto pressure differentials. In other words, where a metering spring isemployed (e.g., metering spring 52 in FIG. 1) it need only provideenough biasing force to return the metering lever to its home positionto close the metering valve. Some other types of metering systemsrequire additional biasing force to hold the metering valve closedagainst the weight of a heavy contact element while the carburetor isnot operating. These are but a few of the possible benefits of layeredmetering diaphragms, and skilled artisans will realize others.

In one embodiment, the metering spring may be omitted altogether, andthe discontinuous layer can provide the biasing force for the meteringlever or other metering system component to keep the metering valveclosed. In this embodiment, the metering lever or other metering systemcomponent may be attached to the metering diaphragm so that diaphragmmovement is translated directly to the attached metering systemcomponent to open and close the metering valve. In this case, thecharacteristic spring rate of the discontinuous layer may be about thesame or higher than the spring rate of a conventional metering spring.In some of the embodiments described below, where an electric ormagnetic field is employed to affect diaphragm movement, a highereffective spring rate for the discontinuous layer may allow for higherresolution control of diaphragm movement (i.e., for a given change inelectric or magnetic field, the corresponding change in the diaphragmmovement is less with a stiffer discontinuous layer).

As shown by example in FIGS. 5-23, discontinuous layers of variousconfigurations may be employed to affect diaphragm movement. FIG. 5shows the discontinuous layer 62 from FIG. 2 in plan view with the threespiral slots 72 formed therethrough and arranged in a pattern about thecentral contact portion 76. When assembled as part of a meteringdiaphragm as described above, the continuous layer applies a force tothe discontinuous layer 62 and moves the contact portion 76 in adirection to actuate the metering valve. The contact portion 76 of layer62 moves out of plane from the remainder of the layer 62 in the mannerof a variable diameter coil spring and can move in the oppositedirection when metering chamber pressure is increased by incoming fuel.

Referring to FIG. 6, another embodiment of a discontinuous layer 162 isshown with a plurality of radially oriented slots 172 formedtherethrough. As with the three-slotted spiral configuration of FIG. 5,slots 172 are arranged in a pattern about the contact portion 176 foreven load distribution across the layer 162 during deflection. Thisconfiguration may also be described as having a plurality of spokes 180extending radially outward from the contact portion 176 within theintended periphery 36 of the metering chamber.

FIG. 7 illustrates another example of a discontinuous layer 262. Thisembodiment includes a pair of larger arc-shaped slots 272 arranged in asymmetric pattern about the contact portion 276. In this embodiment, amajority of the area of the discontinuous layer 262 within the intendedperiphery 36 of the metering chamber is slotted or open area. Thisconfiguration may also be described as having a pair of spokes 280extending radially outward from the contact portion 176. Describeddifferently, the discontinuous layer 262 may be a layer of materialhaving a cut-out 272 that corresponds with the intended periphery 36 ofthe metering chamber and a strip of material 280 spanning the cut-outfrom one side to the other. The strip of material may span the cut-outat a location that does not pass through the center of the cut-out, aswell, depending on the corresponding location of other metering systemcomponents.

Turning to FIG. 8, another embodiment of a discontinuous layer 362 isshown. In this embodiment, a single slot 372 occupies most of the areawithin the intended periphery 36 of the metering chamber and isgenerally C-shaped. This configuration may also be described as a layerof material having a cut-out 372 that corresponds with the intendedperiphery 36 of the metering chamber and a segment of material 380extending from an edge of the cut-out 372 toward the interior of themetering chamber and ending at contact portion 376. In anotherembodiment, the discontinuous layer may include of a segment of materialextending from the periphery of the metering chamber toward the interiorof the metering chamber, and the layer does not necessarily includeother portions that surround the metering chamber at its periphery. Asillustrated in FIG. 8, the open areas of the discontinuous layer neednot be arranged symmetrically or in any repeating pattern, and solidportions of the discontinuous layer need not extend all the way acrossthe metering chamber in order to realize one or more of the benefits ofthese teachings.

Metering diaphragms may also be configured to selectively affectmetering system component movement through means other than meteringspring stiffness, metering lever positioning, or the characteristicspring rate of the discontinuous layer. For example, electric and/ormagnetic fields can be employed to affect metering diaphragm movementwith certain embodiments of layered metering diaphragms. Similararrangements may be used to monitor diaphragm movement or othercarburetor operating characteristics, as well. As will become apparentbelow, affecting diaphragm movement by application of electric ormagnetic fields may be accomplished whether or not the meteringdiaphragm has a layered construction.

Referring to FIG. 9, one embodiment of a discontinuous layer 462 thatcan be affected by an electric and/or magnetic field during operation isillustrated. Dual spiral slots 472 are formed through layer 462 withinthe intended periphery 36 of the metering chamber in this example. Layer462 also includes a conductive portion 490, which in this case is aconductive path. In this embodiment, the conductive path 490 is in theform of electrically conductive traces at a surface of the layer,arranged between the spiral slots 472. Such traces may be included aspart of the discontinuous layer 462 in various forms. In one example,stamped metal traces or pre-formed wires are molded into an otherwiseplastic discontinuous layer. In another example, the conductive path isformed by selective masking and plating or by some other form of metaldeposition. The conductive path 490 may lie at the surface of one sideof the layer 462, extend through the layer so that it is present at bothsides of the layer 462, or be at least partly encapsulated between theopposite surfaces of the layer 462. The conductive path 490 ispreferably insulated from the carburetor body when assembled, though oneend of the path such as end 492 may be in electrical contact with thecarburetor body as a voltage reference point or ground. One or both ends492, 494 may be configured to accommodate electrical connections.

This and other embodiments of discontinuous layers that include aconductive portion may be useful for a variety of metering systemcontrol and/or monitoring techniques. For example, an electric field inthe form of a voltage potential may be selectively applied across ends492, 494 of the conductive path 490, thereby imparting the discontinuouslayer 462 with a different resistance to movement (i.e., characteristicspring rate) than when no voltage potential is applied. The differentvoltage-induced spring rate may arise through various mechanisms such aslocalized interaction among electromagnetic fields surrounding theconductive path where different portions of the path run adjacent to oneanother. Applied voltage may be in one or more steps (e.g., on or off)or continuously variable and may be monitored by a vehicle controlsystem or fuel system controller for selective application andadjustment.

A voltage potential applied to the conductive path 490 may also serve asa metering system heat source—i.e., the conductive path may act as aresistance heater. Controlled heating of the discontinuous layer in thismanner may also affect the characteristic spring rate of thediscontinuous layer and thus its resistance to movement in response tomovement of the continuous layer. For example, a plastic discontinuouslayer including a conductive path 490 such as that shown in FIG. 9 mayhave its effective stiffness reduced or otherwise changed by having itstemperature increased through resistance heating via the conductive path490.

Electrical connections at ends 492, 494 may also be used to monitor oneor more characteristics of the metering system. For example, theconductive path 490 may include a sufficiently thin layer of conductivematerial so that it acts as a strain gauge for the discontinuous layer462. Thus, movement of the discontinuous layer 462 and/or correspondingmetering system components may be monitored in real-time when connectedto a vehicle or fuel system controller. In another embodiment, theconductive path 490 includes more than one layer of conductive materialincluding different types of conductive materials in different layers.This type of configuration may be used as a temperature sensor or as anadditional way to affect the characteristic spring rate of thediscontinuous layer when a voltage potential is applied.

In another implementation, the electrical resistance and/or capacitanceof the conductive portion of the discontinuous layer may be measured andcould be used to help determine certain fuel characteristics in themetering chamber. This is a variation of applying a voltage potentialacross the conductive portion, though the voltage may be of a differentmagnitude than that applied for purposes of heating or changing thecharacteristic spring rate of the discontinuous layer. Resistance orcapacitance measurements obtained in this manner could be used todetermine whether liquid or vapor is present in the metering chamber orcould be correlated to percentage of ethanol composition, for example.

In yet another embodiment, the conductive portion 490 includes aferromagnetic material, so that the movement of the discontinuous layer462 is responsive to a magnetic field provided by a magnetic fieldsource such as a magnet or an electromagnet. The conductive portion inthis case may include a ferromagnetic grade of stainless steel, forexample. In this case, the discontinuous layer does not necessarilyinclude a discrete conductive path and may instead be made from amaterial such as an appropriate stainless steel or an iron-filledplastic material. In either case, the magnetic field source may beincluded as part of the carburetor at a location such that thediscontinuous layer operates at least partly within the magnetic fieldemanating from the source. In one embodiment, an electromagnet isattached to a diaphragm cover (such as cover 30 of FIG. 1). Theelectromagnet may be energized by an applied voltage and/or the magneticfield that it produces may be variable to variably affect the movementof the discontinuous layer. For example, a stronger magnetic fieldpresent at the reference side of the metering diaphragm may cause thediscontinuous layer to have a higher resistance to movement toward themetering lever when in the presence of a weaker or no magnetic field. Inanother embodiment, the magnetic field may be selectively applied to themetering diaphragm to uncork the metering valve during start-up.

FIG. 10 illustrates another example of a discontinuous layer 562including spiral slots 572 of different sizes and a conductive path 590in the form of two spiral arms 580 that extend in a spiral pattern fromopposite sides of the intended periphery 36 of the metering chambertoward the contact portion 576. In this example, the spiral armextending from one side (the right side in FIG. 10) of the intendedperiphery 36 is wider than the spiral arm extending from the opposite(left) side. The overall spiral pattern thus includes alternating wideand narrow portions radially between the intended periphery of themetering chamber 36 and the contact portion 576.

When a voltage potential is applied across the conductive path 590, theresulting current flow through the interlaced wide and narrow portionsof the spiral may be such that adjacent portions of the conductive path590 (separated by slots 572) carry current in opposite directions fromeach other. This induces opposing magnetic fields in adjacent portionsof the conductive path 590. Combined with the different stiffness ofeach adjacent portion, due to the different widths, a twisting orskewing effect may result, wherein the spiral arms 580 twist out ofplane and cause the contact portion to move out of plane as well. Thisis an example of an electric field being employed to affect diaphragmmovement in a manner somewhat different than by affecting thecharacteristic spring rate of the discontinuous layer. This type ofdiaphragm movement in response to induced magnetic fields may be usefulto change the position of the discontinuous layer even when thecarburetor is not operating to provide fuel to the engine. For example,this type of diaphragm movement could be used to uncork the meteringvalve at start-up or as an alternative or addition to traditional primerassemblies. The characteristic spring rate of the discontinuous layer562 may also be affected by voltage application.

These and other layered metering diaphragm configurations may be usedtogether with selective application of both electric and magnetic fieldsto monitor and/or tune a layered metering system without the need todisassemble the carburetor to do so. In one example, a conductiveportion of the discontinuous layer comprises a ferromagnetic material,and the carburetor includes a magnetic field source that can selectivelyand/or variably provide a magnetic field in which the metering diaphragmoperates. The movement of the diaphragm is monitored during carburetoroperation by monitoring the change in resistance of the conductive path.A voltage potential is selectively applied across the conductive pathand/or the magnetic field source is selectively applied to affect themovement of the diaphragm.

A monitoring or control system need not be a complex electronic orcomputer-based system in order to realize any of the benefits of thesefield-affected metering diaphragms. In some cases, it may be preferablethat a voltage potential applied across the conductive path be directlyuser-adjustable by a dial-type potentiometer or other means so that theuser can affect the carburetor air-fuel ratio, for example, duringengine operation and tune the metering system for the particularoperating conditions at the time of use. In some cases, no voltagepotential is applied to the diaphragm during normal operation and theconductive path is provided as a diagnostic tool that can allow a useror technician to check the operation of the metering system withoutdisassembling the carburetor. Skilled artisans will of course recognizeother benefits associated with these and other embodiments. In addition,it is noted that one or more conductive portions may be included as anypart of the metering diaphragm to affect diaphragm movement or for usein monitoring diaphragm movement or other carburetor conditions and arenot limited to discontinuous layers or to layered diaphragmconstructions.

FIGS. 11-14 illustrate other variations of discontinuous layers that maybe used with or without conductive portions as part of a metering systemdiaphragm. The discontinuous layer 662 of FIG. 11 includes contactportion 676 and four segments 680 extending radially from the contactportion to the intended periphery 36 of the metering chamber. Thesegments 680 are equally circumferentially spaced (one every 90 degrees)about the central contact portion 676 forming four identical slots 672between pairs of segments. Each segment 680 forms a serpentine-likeshape, with a generally uniform segment width extending back and forthalong gradually larger arcuate portions from the contact portion 676 tothe intended periphery 36. Of course, the segment widths could vary ifdesired.

FIG. 12 illustrates a discontinuous layer 762 with a contact portion 776and two segments 780 extending radially from the contact portion to theintended periphery 36. The segments 780 are similar to the segments 680of FIG. 11 in their serpentine-like shape, except every other segment680 of FIG. 11 is turned upside-down in plan view and merged with anadjacent segment to arrive at the segments 780 and slots 772 of FIG. 12.

FIG. 13 illustrates a discontinuous layer 862 with a contact portion 876and four concentric ring-shaped segments 880 joined by bridge portions885. Bridge portions 885 between radially sequential segments 880 areoffset 90 degrees from one another, resulting in radially sequentialarcuate slots 872 that are offset 90 degrees from one another.

FIG. 14 illustrates a discontinuous layer 962 with a contact portion976, segments 980, and slots 972 the same as those in FIG. 13. Theillustrated discontinuous layer 962 does not include as much excessmaterial outside the intended periphery 36, as the embodiment of FIG.13, however, and does not include openings that coincide with locatorfeatures of the carburetor body. Layer 962 includes only enough materialoutside the intended periphery 36 to clamp between the carburetor bodyand cover 30 (shown in FIG. 1, for example). Optionally, the entirelayer 962 lies within the metering chamber and is attached in somemanner other than being clamped between the body and cover. Any of thepreviously described discontinuous layers can be shaped similarly sothat they can be assembled in any angular orientation about theirrespective centers.

FIG. 15 illustrates another implementation of a discontinuous layer1062. This example is made in a continuous wire form 1080, with the ends1092 and 1094 of the wire form each including a bend to fit incorresponding openings of the carburetor body at the periphery of themetering chamber. The wire form 1080 is in an interlaced dual-spiralshape, extending and spiraling radially inward from end 1092 to acentral contact portion 1076 and radially outward from the contactportion to end 1094. This wire form configuration may offer certain costadvantages due to less material waste than with stamping operations. Thecircular or otherwise rounded cross-section of the wire form 1080 isalso free from sharp edges that may sometimes be present in piecesstamped from sheets of material, making the wire form configuration lesslikely to abrade or otherwise damage the continuous layer of thediaphragm where the two layers contact each other. The wire form 1080may use any suitable gauge wire in any suitable material. In oneimplementation, the wire form 1080 is formed from metal wire having adiameter in a range from about 0.1 mm to about 1.2 mm. The wire may bemade from stainless steel, a shape memory alloy (e.g. nitinol), or anyother suitable material. The wire form 1080 can be generally flat asshown, with or without bends at the ends 1092, 1094. Or the wire form1080 may be formed so that the wire extends both radially and axiallybetween the contact portion 1076 and the ends 1092, 1094.

FIG. 16 shows the discontinuous layer 1062 of FIG. 15 assembled as partof a carburetor metering system. The continuous layer is omitted forclarity, and the discontinuous layer 1062 is shown at a low meteringchamber pressure condition, where the diaphragm is deflected toward thecarburetor body 14. FIG. 16 also shows one example of how an end 1094 ofthe wireform 1080 may fit within a blind bore 1095 in the carburetorbody at the periphery of the metering chamber 28. When constructed froma conductive material and/or when constructed to include a conductiveportion, the effective spring rate or resistance to movement of layer1062 may be affected by application of an electric or magnetic field asdescribed above.

FIGS. 17-23 illustrate other wire form versions for the discontinuouslayer of the diaphragm. FIG. 17 illustrates an example of adiscontinuous layer 1162 made from two separate wire forms 1180, 1180′.Each wire form is spiral-shaped, extending radially from respective ends1192 and 1194 toward a central contact portion (omitted in FIG. 17 forclarity) where each wire form 1180, 1180′ ends. FIGS. 18 and 19illustrate two examples of fasteners with contact portions 1176 and1176′ that may function to hold the two wire forms 1180, 1180′ together.

The example of FIG. 18 includes a fastener with a contact portion 1176,the fastener having an S-shaped post for each wire from 1180, 1180′ towrap partly around and/or snap into as shown. FIG. 20 is across-sectional view taken through the contact portion 1176 of FIG. 18.The fastener may be a molded plastic piece, such as acetal, or can bemade from any other suitable material.

The example of FIG. 19 includes a fastener with a contact portion 1176′,the fastener being in the form of a rivet, as shown in thecross-sectional view of FIG. 21. A solid rivet is shown, but a hollowrivet could be used instead. A metal rivet may be preferred inembodiments where electrical contact is desired at the contact portionfrom electrical continuity between the ends 1192, 1194. Other variationsof the examples of FIGS. 17-19 include the use of different gauge wire,a different material, or different shapes for each separate wire form1180, 1180′, any of which may affect diaphragm movement either with orwithout an applied electric or magnetic field. The fastener joining thewire forms 1180, 1180′ could also be insert-molded plastic, heat-stakedplastic, sonic or ultrasonic welded pieces, or snap-together pieces, toname a few examples.

FIG. 22 illustrates another example of a discontinuous layer 1262 madefrom two separate wire forms 1280, 1280′. Together, the wire forms 1280,1280′ are similar in shape to the segments 680 of FIG. 11. Each wireform 1280, 1280′ has a serpentine-like shape beginning at a first end1292, 1292′, extending back and forth along gradually smaller arcuateportions radially toward the central contact portion 1276, and thenextending back and forth along gradually larger arcuate portionsradially toward the intended periphery and a second end 1294, 1294′. Thetwo separate wire forms 1280, 1280′ can be identical shapes and may bejoined at the contact portion 1276 by a spot weld, a clip, or otherfastener. In this example, the ends of the wire forms do not includebends, but extend slightly beyond the intended periphery of the meteringchamber where they may fit into complimentary slits or slots formed inthe continuous layer and/or the gasket about the periphery of thechamber. The two wire forms 1280, 1280′ may have different wire gauges,different materials, or be different shapes (e.g. a different number ofarcuate portions).

FIG. 23 illustrates another example of a discontinuous layer 1362 madefrom a single wire form 1380. The wire form 1380 includesserpentine-like shapes beginning at end 1392, extending back and forthalong gradually smaller arcuate portions radially toward the centralcontact portion 1376, and then extending back and forth along graduallylarger arcuate portions radially toward the intended periphery and end1394. In this example, the ends of the wire form 1380 do not includebends, but extend slightly beyond the intended periphery of the meteringchamber where they may fit into complimentary slits or slots formed inthe continuous layer and/or the gasket about the periphery of thechamber.

In FIG. 24, one implementation of a metering system 12 is illustratedthat utilizes a larger portion of the overall movement of the meteringdiaphragm 40 than is conventional. In this example, the metering lever48 is constructed and arranged so that it is in contact with themetering diaphragm 40 for a majority of the total range of movement ofthe diaphragm 40. The metering diaphragm 40 is depicted as a singlelayer of material in FIG. 24, as this arrangement is applicable tometering diaphragms with any number of layers, with or without adiscontinuous layer. The range of movement of the diaphragm 40corresponds to the difference in diaphragm location from a minimum to amaximum operating volume for the metering chamber 28. In FIG. 24, themaximum operating volume of the metering chamber 28 is reached when thediaphragm 40 is at position M (high pressure chamber condition), and theminimum operating volume of the metering chamber 28 is reached when thediaphragm is at position M′ (low pressure chamber condition). Themetering lever 48 is configured so that it extends past the midpoint ofthe total range of movement when the metering valve is closed in orderto utilize more than half of the total diaphragm stroke. In analternative configuration, the diaphragm includes a contact portion thatremains in contact with the metering lever 48 for the majority of thediaphragm stroke whether or not the metering lever 48 ever extends pastthe midpoint of the stroke.

This type of configuration may be particularly useful with certaindiaphragm constructions that do not necessarily include an annularconvolution or a bagged portion. For example, layered diaphragmconstructions such as those described above facilitate the use ofdiaphragm materials such as PTFE with increased resistance to modernfuels compared to rubber-based materials. As a continuous layer 60 infilm form, however, such materials may not be as flexible asrubber-based materials, particularly in the absence of a convolution,thus reducing the range of movement of the diaphragm. Utilizing amajority of the range of movement of the diaphragm 40 as shown in FIG.24 or in a similar manner can help ensure proper uncorking of themetering valve during purging at start-up. In one embodiment, themetering lever 48 or other metering system component is attached to thediaphragm 40 so that all of the range of movement of the diaphragm 40 isutilized.

Turning now to FIG. 25, there is shown a cross-section of one example ofa diaphragm fuel pump 20 to demonstrate another useful implementation ofa layered diaphragm. The particular fuel pump 20 shown in the figure isformed between the main body 14 and the intermediate body 15 of thecarburetor, as described in connection with FIG. 2. Here, diaphragm 140separates a pump chamber 128 from a pulse chamber 130, with oppositesides of the diaphragm each defining a portion of the pump and pulsechambers. The pulse chamber 130 alternates between high and low pressurestates through fluid connection with a pulse source, such as an enginecrankcase, via passage 116. The illustrated fuel pump is shown with thepulse chamber 130 in the low pressure state so that the diaphragm 140 isdeflected in a direction that increases the volume of the pump chamber128. In response, fuel flows from an external source into inlet 118,through open inlet valve 142, and into the pump chamber 128, duringwhich time outlet valve 144 is closed. The dashed lines of FIG. 25depict the diaphragm 140 and the valves 142, 144 in their respectivepositions when the pulse chamber is at the high pressure state. At thehigh pressure state, the inlet valve 142 closes, the outlet valve 144opens, and the diaphragm 140 deflects in a direction that decreases thevolume of the pump chamber 128, resulting in fuel flow from the pumpchamber to passage 18 and toward the metering chamber 28 (not shown).

The fuel pump diaphragm 140 is shown schematically here as a layer ofmaterial that is fixed at a periphery 136 of one or both of the pump andpulse chambers 128, 130. For example, one or more layers of thediaphragm 140 may be clamped between bodies 14, 15 as many of theabove-described metering diaphragms are clamped between a carburetorbody and cover. In accordance with the above-described meteringdiaphragms, the fuel pump diaphragm 140 may include a continuous layerand a discontinuous layer and realize at least some of the sameadvantages. Here, the pump chamber 128, fuel pump diaphragm 140, andinlet valve 142 are respectively analogous to the metering chamber,diaphragm, and metering valve of the above-described metering systems.Similarly, the fuel pump diaphragm 140 may include a discontinuous layerthat is attached at the periphery 136 of either or both chambers 128,130 that can impart the diaphragm with a resistance to movementdependent on one or more factors, such as the amount of diaphragmmovement or the presence, application, and/or magnitude of an electricor magnetic field. The diaphragm 140 can include a discontinuous layerwith one or more slots, conductive portions, wireforms, etc. Rather thanbeing attached at periphery 136, the discontinuous layer of the fuelpump diaphragm may lie entirely within the periphery of chambers 128,130. For example, the discontinuous layer may be a thin layer of metaladhered to, plated onto, or otherwise affixed to the continuous layer ofthe fuel pump diaphragm.

For example, a discontinuous layer with a conductive portion may beconfigured to affect fuel pump diaphragm movement independently orcomplimentary to the movement induced by the pulse source. In oneembodiment, the fuel pump diaphragm is configured to operate—i.e., todeflect back and forth to pump fuel through the pump chamber 128—in theabsence of a pulse source. In other words, the diaphragm 140 may includea discontinuous portion that moves in response to an applied magnetic orelectric field, and the application of the field can be controlled tocontrol diaphragm movement and fuel pump operation. The fuel pumpdiaphragm 140 does not necessarily contact other moving components likethe analogous metering diaphragm does (i.e., the metering lever), andthe discontinuous layer can thus be located on either the pump chamberside of the diaphragm or on the opposite side of the diaphragm, or onboth sides. This may also eliminate any need for a contact portion ofthe discontinuous layer.

Referring now to FIGS. 26 and 27, there is shown an illustrative processfor making a metering diaphragm 40 having a continuous layer 60 and adiscontinuous layer 62. This process is applicable to multi-layer pumpdiaphragms as well. FIG. 26 is a side view of the process, and FIG. 27is a plan view. In this process, layers 60 and 62 are attached togetheras a subassembly and/or are manufactured together rather than beingprovided as separate pieces. In this example, the materials 60″ and 62″for both of the layers 60 and 62 are provided in strip or sheet form andfed in a machine direction A. Material 62″ is fed in direction A andslots 72 are formed through the material at step (a), along withindexing or alignment holes arranged along the edges of the material. Inthis embodiment, the slots 72 are in the spiral configuration of FIG. 5.Material 60″ is then fed to overlap with material 62″, between theindexing holes in this example. The material 60″ may include a layer ofadhesive on the side that opposes and contacts the material 62″. Theadhesive may be, for example, pressure sensitive and/or heat activated.

A bonding tool presses the two materials together at step (b). Thebonding tool is configured so that pressure and/or heat is applied to anarea of the overlapping materials that is outside of the formed slots72. In this example, heat and/or pressure is applied within area75—i.e., the area between the dashed lines in FIG. 27. The diaphragm 40is then cut to shape from the layered and bonded materials at step (c),at which time other holes or locating features 74 may also be formed.The finished diaphragm 40 as oriented in FIG. 27 has the continuouslayer 60 on top and the discontinuous layer 62 on bottom.

Consistent with the above description, the respective materials 60″ and62″ may be selected with their individual functions in mind. Forexample, material 60″, which forms the continuous layer 60, may be athin, flexible layer with high resistance to hydrocarbon fuels with orwithout alcohol content. In one example, the material 60″ is a filmcomprising a fluorinated polymer such as PTFE, perfluoroalkoxy (PFA) orfluorinated poly(ethylene-propylene) (FEP). In one embodiment, the film60″ is about 0.001″ in thickness, but may vary depending on the materialtype and other factors. Where included, the adhesive layer may have aheat activation temperature below the softening point, melting pointand/or glass transition temperature of the material 60″ so that it canbe heat-activated without melting, shrinking, or otherwise damaging thematerial. The adhesive layer may also be selected to be soluble in theparticular fuel to be used in the carburetor assembly so that excessadhesive is removed from between the layers 60, 62 during carburetoroperation. One suitable adhesive layer material is an acrylic-basedadhesive. Material 62″ may be metallic, such as stainless steel oraluminum, or polymeric, such as Mylar® or other polyester-based film. Inone embodiment, the material 62″ is a polymeric film having a thicknessof about 0.010″.

Where employed, the adhesive layer may be included with thediscontinuous layer material 62″ in addition to or instead of thecontinuous layer material 60″. If it is desired to include a baggedportion (such as portion 65 of FIG. 3) in the continuous layer 60, thediscontinuous layer material 62″ can be formed with a dome or raisedportion at step (a) or some other step prior to bringing the continuouslayer material 60″ into contact therewith so that the thinner continuouslayer material is stretched over the formed material 62″. Theillustrated process is illustrative, as some steps may be omitted and/oradditional steps may be added. For example, a tape or other temporaryattachment may be used to hold the two layers of material 60″, 62″together prior to bonding. The bonding may be performed withoutadhesive, such as by heat staking, ultrasonic welding, or any othersuitable technique, and it is not always necessary to achieve a fullsurface bond outside of the slotted portion of the discontinuous layer62.

The process provides a diaphragm assembly that can be easily handled ina manufacturing environment. With the multi-layer diaphragm describedherein, where individual layers of the diaphragm may be made to performtheir individual functions better than any single layer could performthe combined functions, material handling during manufacturing may be anew consideration. For example, the above-described diaphragm may employa very thin polymeric film as the continuous layer, and such thin layerscan be difficult to handle—i.e., a 0.001″ layer of polymer may easilyfold or wrinkle and static charges can develop if handled as a separatepiece. Providing the diaphragm 40 as a bonded or laminated subassemblythat includes the discontinuous layer as well can provide a sturdierpiece for handling in the carburetor manufacturing environment.

FIGS. 28-30 illustrate a dynamic portion 150 of a diaphragm fuel pump.When assembled (see FIG. 25), the dynamic portion 150 is clamped betweentwo fuel pump bodies 14, 15 and includes the fuel pump diaphragm 140 andone or more valves 142, 144, where the valves are flapper valves. Theillustrated dynamic portion 150 is a multi-layer assembly and may bemanufactured in a manner similar to that shown in FIGS. 26 and 27, withor without a discontinuous portion included with the diaphragm 140. Themulti-layer dynamic portion 150 may realize some of the same advantagesas the examples of multi-layer diaphragms described above in that eachlayer can be constructed with its individual function in mind.

FIG. 28 shows the dynamic portion 150 in plan view, FIG. 29 is across-sectional view of the diaphragm 140 when assembled into thecarburetor, and FIG. 30 is a cross-sectional view of a flapper valve142, 144 when assembled into the carburetor. The dynamic portion 150includes a sealing layer 152 and a support layer 154. As shown in FIG.29, a portion of the sealing layer 152 becomes the diaphragm 140 whenclamped between carburetor bodies 14, 15, separating the pump and pulsechambers of the fuel pump. As shown in FIG. 30, other portions of thesealing layer 152 become the sealing or valve seat side of each flappervalve 142, 144. The support layer 154 is omitted at the diaphragm 140 inthis example and is present on the opposite or non-sealing side of eachvalve 142, 144. This configuration allows the diaphragm 140 to be formedfrom a relatively thin and flexible film or membrane, for increasedresponse to pressure differentials, while the valves 142, 144 can beformed with sufficient operating integrity.

For example, sealing layer 152 can be formed from a thin polymeric filmwith good resistance to hydrocarbon fuels, ethanol, water, and acid tofulfill the requirements for diaphragm 140. In one embodiment, thesealing layer 152 is a fluorinated polymeric film, such as PTFE, PFA orFEP, with a thickness ranging from 0.001″-0.002″. Taken alone, such athin polymeric membrane may have difficulty functioning as a flappervalve or may not be strong enough for repeated cycling, due to lack ofrigidity or structure. Support layer 154 can provide the flapper valves142, 144 with sufficient stiffness or integrity. The support layer canbe a layer of metallic or polymeric material (e.g., stainless steel,aluminum, Mylar, Delrin, etc.) having a thickness sufficient to providethe valves 142, 144 with enough stiffness or integrity to open and closeproperly. In one embodiment, the support layer 154 is a layer ofpolymeric film having a thickness of about 0.005″. The support layer 154also provides the dynamic portion 150 of the fuel pump with sufficientintegrity to be handled in a manufacturing environment without easilyfolding or wrinkling, as may be the case if the dynamic layer was asingle layer of flexible polymeric film optimized for diaphragmflexibility.

The dynamic portion 150 can be made in a process similar to that shownin connection with the metering diaphragm process of FIGS. 26 and 27,where the support layer 154 first has an opening formed therethroughcorresponding to the outer periphery of the diaphragm 140, and thesealing layer 152 is subsequently bonded with the support layer prior tothe final dynamic portion 150 being cut from the layered materials.

FIG. 31 illustrates another implementation of a multi-layer diaphragm200 shown implemented as a fuel metering diaphragm such as may be usedin a carburetor 202, which may be like that disclosed above. Thediaphragm 200 may include a continuous layer 204, which may beconstructed and arranged in the same manner as the continuous layerspreviously described and a discontinuous layer 206 which may also beconstructed and arranged in the same manner as the discontinuous layerspreviously described. In addition, the diaphragm 200 may have anintermediate layer 208.

The intermediate layer 208 may be received between the continuous layer204 and the discontinuous layer 206 and arranged to prevent orsubstantially inhibit direct contact of the discontinuous layer with thecontinuous layer. The intermediate layer 208 may thus act as a bufferbetween the other layers 204, 206. In at least some implementations, theintermediate layer 208 may be formed from a softer or less abrasivematerial compared to the discontinuous layer 206, and this may reducewear on and extend the useful life of the continuous layer 204. In thisway, the intermediate layer 208 may be provided with a contact portion210 that is of a size and orientation to limit or prevent contact of thediscontinuous layer 206 with the continuous layer 204. Where thediaphragm 200 is trapped about its perimeter between two bodies (e.g. acover 212 and a main body 214 of the carburetor 202), the contactportion 201 may be arranged in or near the center of an exposed area ofthe intermediate layer 208, where the exposed area is the portionradially within a perimeter portion 216 that is trapped between the twobodies 212, 214 in assembly. The center of the exposed area of theintermediate layer 208 (and the continuous and discontinuous layers 204,206) is the region of greatest displacement or movement in use, andusually is the area used to actuate the metering valve 42 (not shown inFIG. 31). Accordingly, this is usually the area where the metering valvelever is arranged for engagement by a contact portion 218 of thediscontinuous layer 206 as noted above.

The intermediate layer 208 may be formed of any desired material, andmay be constructed and arranged like the discontinuous layer 206, withone or more voids 220 formed therein through which fluid (e.g.atmospheric air in this example) may pass and act on the continuouslayer 204. As described above with regard to the discontinuous layer,the intermediate layer 208 may include one or more voids, a segment ofmaterial, or a wire form, where the wire form may be provided from anydesired material. In at least some implementations, the intermediatelayer 208 is formed generally complementarily to the discontinuous layer206 so that the intermediate layer overlaps at least a majority of thediscontinuous layer, and up to all of the contact portion 218 of thediscontinuous layer. Further, portions of the intermediate layer 208 maypartially overlap at least some of the void(s) 222 formed in thediscontinuous layer 206. This may help to ensure that the discontinuouslayer 206 does not directly engage, to any significant extent, thecontinuous layer 204, and it may also help to ensure that theintermediate layer and discontinuous layer do not become interlocked ortangled (e.g. portions axially overlapped). This also inhibits orprevents the intermediate layer 208 from engaging the metering valvelever. In at least some implementations, the intermediate layer 208 maybe formed from a softer material and engagement with the metering valvelever may unduly wear or damage the intermediate layer. Thus, thediscontinuous layer 206 protects the intermediate layer 208 and thecontinuous layer 204 from contact with the metering valve lever. And theintermediate layer 208 protects the continuous layer 204 against most orall direct contact with the discontinuous layer 206.

In the example shown in FIG. 31, the intermediate and discontinuouslayers 208, 206 include radial spirals (which may be formed, forexample, like that shown in FIGS. 2-5, or otherwise as desired) and thespiral segments 224 of the intermediate layer 208 are radially wider,and may be fewer in number (e.g. fewer turns) than the segments 226 ofthe discontinuous layer 206. In this way, no significant and contiguouslength of the discontinuous layer 206 is not overlapped by theintermediate layer 208 which reduces the likelihood that any portion ofthe discontinuous layer 206 will pass into or through a void 220 in theintermediate layer 208 and become axially overlapped with theintermediate layer 208. Likewise, this prevents or inhibits portions ofthe intermediate layer 208 from axially passing through a void 222 inthe discontinuous layer 206 where that portion of the intermediate layermay engage the metering valve lever. Even though the spiral of theintermediate layer 208 is defined by thicker (e.g. radially wider)portions of material, the intermediate layer 208 may be formed from amore flexible and softer material than the discontinuous layer 206, sothe movement of the continuous layer 204 is not unduly inhibited by theintermediate layer 208 and can be effectively transmitted to thediscontinuous layer 206 for effective actuation of the metering valve.

In addition to providing a buffer between the continuous anddiscontinuous layers 204, 206, the intermediate layer 208 may also beformed of a material that is lighter. The lighter material may have lessmass and may move axially and radially less under vibrations that may beexperienced by and within the carburetor 202. This may reduce themovement relative to the continuous layer 204 compared to the movementof the discontinuous layer 206, and this may further reduce wear on thecontinuous layer 204. Also, the softer and lighter material of theintermediate layer 208 may have a smoother surface finish than thediscontinuous layer 206 which further reduces wear on the continuouslayer 204. When stamped to provide the voids therein, edges of theintermediate layer 208 may have a larger radius compared to edges of thediscontinuous layer 206. To reduce wear on the continuous layer 204, thetrailing edge of the stamped intermediate layer may be oriented facingthe discontinuous layer. This makes the intermediate layer edges lesssharp which also reduces wear on the continuous layer 204. Theintermediate layer could also be molded or formed by a chemical etchingprocess. A representative surface finish for the intermediate layer isnot greater than RA 20 microinch.

Suitable materials for the intermediate layer 208 includeperfluoroalkoxy (PFA), polytetraflouroethylene (PTFE), fluorinatedEthylene Propylene (FEP), polyester, fluoroelastomer, low densitypolyethylene, nitrile rubber, or polyurethane. The intermediate layermay have a thickness in the range of 0.0254 mm to 0.381 mm (0.001 of aninch to 0.015 of an inch) and desirably about 0.127 mm to 0.254 mm(0.005 of an inch to 0.010 of an inch).

In the example shown, the periphery 216 of the intermediate layer 208 istrapped between the peripheries of the continuous layer 204 anddiscontinuous layer 206, and perhaps one or more seals or gaskets 228,which are all sandwiched between the bodies 212, 214. The intermediatelayer 208 could instead be received between the continuous anddiscontinuous layers 204, 206 without a periphery separately trappedbetween the carburetor bodies 212, 214. For example, without limitation,the intermediate layer 208 may be loosely received between the layers204, 206, or connected to only a portion of a layer 204 or 206, orconnected to the body/cover 212, 214 along only a segment and not acontinuous periphery 216. In at least some forms, the intermediate layer208 is maintained separate from (i.e. not connected or bonded to) thediscontinuous layer 206, but it could be at least partially connected orbonded thereto. Also, the intermediate layer 208 could be fully attachedto the discontinuous layer 206 and may be bonded thereto (such as by anadhesive, welding, heat shrink connection, or by coating at least aportion of the discontinuous layer with a material defining theintermediate layer). The intermediate layer 208 may overlap only aportion of the discontinuous layer 206, such as the portion or portionsthat may engage the continuous layer 204 in use. Further, while noted asbeing bonded or coupled to the discontinuous layer 206, in someimplementations the intermediate layer 208 may be bonded or coupled tothe continuous layer 204. The intermediate layer 208 may overly some orall of the exposed area of the continuous layer 204, or just a portionor portions that may be contacted by the discontinuous layer 206 in use.

While the forms of the invention herein disclosed constitute presentlypreferred embodiments, many others are possible. It is not intendedherein to mention all the possible equivalent forms or ramifications ofthe invention. It is understood that the terms used herein are merelydescriptive, rather than limiting, and that various changes may be madewithout departing from the spirit or scope of the invention.

The invention claimed is:
 1. A carburetor having a metering system thatcontrols fuel flow from a fuel source to an air-fuel passage, themetering system comprising: a metering assembly including a meteringvalve and a metering diaphragm sealed to a body of the carburetor to atleast partly define a metering chamber between the metering diaphragmand the body, the metering diaphragm having a portion that is moveablerelative to the body to actuate the metering valve, and the meteringdiaphragm including a continuous layer, a discontinuous layer and anintermediate layer received at least partially between the continuouslayer and the discontinuous layer; wherein the continuous layer isresponsive to fluid pressure to move the discontinuous layer to open ametering valve to allow fuel flow from the fuel source into the meteringchamber.
 2. The carburetor of claim 1, wherein the intermediate layerincludes a periphery trapped between two carburetor bodies and between aperiphery of the continuous layer and a periphery of the discontinuouslayer.
 3. The carburetor of claim 1, wherein the intermediate layerincludes a void, a segment, or a wire form.
 4. The carburetor of claim 1wherein the intermediate layer is formed from a material that is softerthan the discontinuous layer.
 5. The carburetor of claim 1 wherein theintermediate layer substantially inhibits direct contact between thecontinuous layer and the discontinuous layer.
 6. The carburetor of claim1 wherein the intermediate layer has portions underlying at leastportions of the discontinuous layer and voids complimentary to voids inthe discontinuous layer.
 7. The carburetor of claim 1 wherein at leastportions of the intermediate layer underlying at least portions of thediscontinuous layer have a radial width greater than the radial width ofthe portions of the discontinuous layer they underlie.
 8. The carburetorof claim 1 wherein the discontinuous layer includes a portion protectingthe intermediate layer and the continuous layer from contact with ametering valve lever.
 9. The carburetor of claim 1 wherein thecontinuous and discontinuous layers are of different materials and theintermediate layer is of a material different than the material of thediscontinuous layer.
 10. The carburetor of claim 1 wherein theintermediate layer comprises a less abrasive material than that of thediscontinuous layer.
 11. The carburetor of claim 1 wherein theintermediate layer comprises at least one of a perfluoroalkoxy (PFA),polytetraflouroethylene (PTFE), fluorinated Ethylene Propylene (FEP),polyester, fluoroelastomer, low density polyethylene, nitrile rubber, orpolyurethane.
 12. The carburetor of claim 1 wherein the intermediatelayer has a smoother surface than the discontinuous layer.
 13. Thecarburetor of claim 1 wherein the surface finish of the intermediatelayer is not greater than RA 20 microinches.
 14. The carburetor of claim1 wherein the intermediate layer is bonded to the discontinuous layer.15. The carburetor of claim 1 wherein the intermediate layer has athickness in the range of 0.0254 mm to 0.381 mm.
 16. A carburetor,comprising: first and second bodies; a fuel chamber located between thefirst and second bodies; a multilayer diaphragm clamped between thefirst and second bodies, the diaphragm comprising a first layer ofdiscontinuous material, a second layer of a continuous differentmaterial and a third layer of material positioned at least partiallybetween the first and second layers of material; and a fuel flow valvethat opens and closes to allow fuel flow into or out of the fuelchamber, wherein the first layer of discontinuous material flexes toselectively actuate the fuel flow valve, and the second layer ofcontinuous material defines a portion of the fuel chamber and moves inresponse to a pressure differential across the second layer ofcontinuous material, and wherein the third layer of material at leastsubstantially inhibits direct contact of the first layer of materialwith the second layer of material.
 17. The carburetor of claim 16,wherein the fuel chamber is a metering chamber, the diaphragm is a fuelmetering diaphragm, the first layer of discontinuous material flexes andengages a valve lever, and the third layer of material is discontinuousand of a material different than that of the first layer of material.